CBSE Class 10 Science 2019 · Paper 31/1/1 · Question 26(a)

Electricity 2 marks Medium

While studying the dependence of potential difference (

V

) across a resistor on the current (

I

) passing through it, in order to determine the resistance of the resistor, a student took 5 readings for different values of current and plotted a graph between

V

and

I

. He got a straight line graph passing through the origin. What does the straight line signify? Write the method of determining resistance of the resister using this graph.

Answer

A straight line through the origin shows $V \propto I$ (Ohm's law); the resistance is the slope $\frac{Δ V}{Δ I}$ of the graph.

The straight line through the origin shows that the potential difference

V

across the resistor is directly proportional to the current

I

through it (

V \propto I

, Ohm's law); so

\frac{V}{I}

, the resistance, is constant. Method: find the slope of the

V

I

graph. Take two points

(I_{1}, V_{1})

and

(I_{2}, V_{2})

on the line, well apart; then

R = slope = \frac{V _{2} - V _{1}}{I _{2} - I _{1}} = \frac{Δ V}{Δ I}

, in ohm.

🔒 Step-by-step solution

CBSE Class 10 Science 2019 · Paper 31/1/1 · Question 26(a)

Answer

From the board papers

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